Solubilised rice bran ferulic acid has potential to retard cooked rice retrogradation and not impact digestibility

Abstract

• Noncovalent binding to trehalose made ferulic acid from rice bran water-soluble. • Solubilised ferulic acid boosted starch thermal aggregation by noncovalent binding. • This led to reduce retrogradation in rice cooked in trehalose-rice bran extract. • However, in vitro digestibility and glycaemic potential of the rice did not rise. This study investigated if solubilised rice bran extract could lessen retrogradation in cooked Hom Mali rice during prolonged storage, and still lower its glycaemic potential. Retrogradation was analysed by differential scanning calorimetry and Raman spectroscopy, while in vitro starch digestibility was tested by the Englyst method. The key findings were: (1) Ferulic acid in the extract interacted noncovalently with gelatinised amylose to promote aggregation, as evidenced by heteronuclear multiple bond coherence and analytical ultracentrifugation, respectively. (2) Rice infused and cooked with the extract exhibited reduced retrogradation after storage at 4 °C over ∼2 weeks, compared to control rice. The reduced retrogradation also translated into lower tendency for syneresis. (3) In vitro starch digestibility of treated rice was lower/not higher than fresh control rice. The findings bear implications on how the textural quality of a high-moisture starch staple could be preserved in prolonged storage, without compromising its nutritional quality.